There are quite a few considerations in such a patient. Profound anemia, cardiopulmonary disorders, and metabolic disorders such as Addison's disease (hypoadrenocorticism) are important differential diagnoses.
Inherited neurologic disorders causing weakness or inherited muscle disorders causing progressive muscle atrophy, weakness, and collapse occur rarely and when they do are mostly seen in young dogs. Partial seizures resembling episodic weakness/collapse are a consideration but, once again, unlikely, considering the history you provided. A video of Cinnamon's behavior is very important for the practitioner to see. Important information includes whether the weakness occurred acutely or was progressive over time; whether there have been any historical or concurrent systemic abnormalities, duration of weakness, mentation/consciousness during the episodes of weakness, activity, and events preceding weakness (e.g., possible triggers).
The physical exam findings which may directly assist diagnosis include:
Pallor, hypotension - active bleeding
Weak femoral pulses, muffled heart sounds, irregular heart rate - cardiac disease
Inspiratory or expiratory dyspnea - pulmonary disease
Abnormalities of proprioception (knowing where one's limbs are in space) and nociception (deep pain perception), and/or reflexes - spinal cord disorder
Neurologic abnormalities - brain disorder
Muscle atrophy, fever, muscle pain, joint pain, bone pain - musculoskeletal disorder
Please respond with further questions or concerns if you wish.